KR20010105314A - Microporous heat-insulating body - Google Patents

Abstract

The microporus heat insulation body consists of a core of a compressed heat insulation material containing from 30 to 90% by weight of a finely divided metal oxide and further additives, wherein one or both surfaces thereof have a cover of a heat-resistant material and where the covers are the same or different and at least one side consists of prefabricated mica sheets.

Description

Microporous Insulator {MICROPOROUS HEAT-INSULATING BODY}

The present invention relates to a microporous insulator consisting of a core of compressed thermal insulation material containing 30-90% by weight of finely divided metal oxides and further additives and coated on one or both sides with a heat resistant material.

Insulators are described, for example, in EP-A-0 618 399, but at least one side of the molded article has a pore base area of 0.01-8 mm ² and a penetration depth of 5-100 based on the thickness of the molded part. It is required to have a channel void of% and the surface of the molded part contains 0.004-10 channel voids per cm ² .

The insulation is produced by gun-pressing the channel voids to be formed by drilling, punching or milling and preferably by embossing punches and then sintering at a temperature of 500-900 ° C. These methods can explode explosive vapors upon rapid heating, avoiding decomposition of the insulation.

Disadvantages of the insulator are the complexity of the manufacturing process and the deterioration of the insulating properties due to gas convection in the voids.

Another method for producing microporous insulation is described in EP-A-0 623 567, wherein SiO ₂ , optionally Al ₂ O ₃ and pyrogenated oxides, hydroxides and carbonates of Group 2 metals of the periodic table Compress with the opacifiers and organic fibers and then sinter at temperatures above 700 ° C. This method is not only complicated, but also has the disadvantage that it takes a long time to recool this well-separated material.

Heat-resistant adhesives and slurries, insulators made from silica sol and mud are described in DE-C-40 20 771. In addition, other prior art relating to the manufacture and composition of insulation is described. A disadvantage of all thermal insulators, including organic components and especially organic fiber materials, is that the organic components are characterized by undesired gas evolution at very high temperatures.

DE 41 06 727 describes an insulator with a plastic seat cover, in which a special shrinkable plastic sheet can be used. These insulators also contain organic materials and dimensional stability is disturbed when severely heated.

DE-C-42 02 569 describes molds for crimping insulation, in particular molds for electric radiation heaters, such as boiling plates.

EP-A-686 732 describes a key-compressed insulating plate made of different inner and outer materials, which material comprises stabilizing openings made entirely of outer material. These plates can also be produced only in complex ways and their mechanical stability and thermal insulation properties are not optimal.

The insulation plate has another drawback that it is difficult to avoid damaging the outer layer during the cutting and processing steps unless a very expensive tool such as a laser cutter can be used to cut off the cut edges of glass.

Methods for the preparation of xonotlite precrystallized with felt and interlaced with each other and their use are known from DE 36 21 705. Bubble-like particles, which are now known to be low in density, are already used to make light insulators. However, xenotrite crystals in the compressed state do not have good thermal insulation properties of the dry-pressed metal oxide.

Another attempt to solve the problem in the manufacture of insulating plates in order to obtain optimum properties is described in EP 0 829 346, which again lists the difficulties and disadvantages of the present technology.

An important problem in the manufacture of insulators by dry pressing of parts is that these materials are elastic and must be at least high pressure to be re-expanded after pressing to obtain useful results.

The bending strength of the thermal insulation plate can be improved by adding fibrous material, but large amounts of fiber tend to increase delamination and worsen the cohesiveness of the compacted mixture during the critical demolding step.

In some cases, the thermal insulation plates must contain organic or vulnerable components, which can result in partial release of toxic gases upon heating to high temperatures. Finally, the finished insulation must be easily machined without any problems, for example to be able to saw, cut or drill the insulation without creating unwanted dust.

Finally, insulation is often required to be a good electrical breaker. However, there are cases where at least one side is desirable to have electrical conductivity capable of dissipating the electrostatic charge.

These problems are all caused by compressed thermal insulation materials containing 30-90% by weight of finely divided metal oxides, 0-30% by weight of opacifiers, 0-10% by weight of inorganic fiber materials and 0-15% by weight of inorganic binders. It was solved by a microporous insulator made of and further comprising 2-45% by weight, preferably 5-15% by weight, of xenonotite. The insulation is the subject of DE 198 59 084.9.

Preferably, the microporous insulator is covered on one or both sides with an insulating material. Particular preference is given to the same or different covers consisting of roughly-pressed xsonotrite, prefabricated mica and graphite sheets. The use of xonotrite and / or mica covers is a good electrical barrier. The use of graphite results in a cover having conductivity that can at least disperse electrical charge. Thus, in some cases it may be advantageous to have one side of the cover made of xenonotrite and / or mica and the other cover made of graphite.

It has now been found that covering porous insulation with prefabricated mica sheets significantly improves the properties of the insulation in two different ways, namely in terms of thermal conductivity and mechanical properties, in particular bending strength. First, this was demonstrated by an internal test of the microporous insulation according to DE 198 59 084.9. However, in addition to covering with prefabricated mica sheets, it has also been demonstrated that other microporous insulations also significantly improve. Accordingly, the subject of the present invention is a microporous insulator consisting of a compressed insulating material core containing 40-90% by weight of finely divided metal oxides and additional additives, one or both sides of which are covered with a heat resistant material and the cover is different. At least one side is made of mica sheet prepared in advance.

Preferably, the cover is made of a mica sheet prepared on both sides in advance.

The core preferably consists of 0-30% by weight opaque agent, 0-10% by weight fibrous material, 0-15% by weight inorganic binder (inorganic fibrous material is preferred).

Above all, it is evident that the mechanical properties are improved in insulators with pronounced flexibility due to thickness. Therefore, the thickness of the heat insulator is preferably 5-7 mm, particularly preferably 3-10 mm.

In addition, insulation with a cover attached to the core has proved to be particularly efficient. As the adhesive, both inorganic adhesives such as water glass and organic adhesives such as polyvinyl acetate are possible. Small amounts of processed organic material do not substantially compromise the material properties when heating the finished microporous insulation.

In principle, it is possible to heat-seal the core and mica sheets together in films, especially shrink films, instead of adhering them. Such microporous insulators also have improved insulation, improved mechanical stability and good bending strengths, for example, over products according to EP-A-0 829 346.

The invention will be illustrated in more detail in the following examples and comparative examples.

Example 1

A mixture of 63% by weight exothermic silicic acid, 30% by weight rutile, 2% by weight silicate fibers (6 mm long) and 5% by weight synthetic xsonotlite was dry-mixed in a mixer and then variously pressed to 0.9-7.0 MPa. Press-pressed in a metal mold by pressure. In this way a plate having a density of 300-560 kg / m ³ was obtained. Bending strength varied from 0.1-0.8 MPa as a function of density. This value is shown in FIG.

In addition, lambda values (thermal conductivity W / (m ° K)) as a function of temperature were measured using hot plates separated according to DIN 52 612.

The plates mentioned above were covered with a 0.1 mm thick mica sheet and bonded with a commercially available organic adhesive based on PVA (polyvinyl acetate). Mica sheets are commercially available from Cogebi, Belgium.

The flexural strength and thermal conductivity of the plates thus obtained were tested. The results are summarized in the following table and shown in FIGS. 1 and 2.

Claims (7)

Comprising a core of pressed insulating material containing 30-90% by weight of finely divided metal oxides and additional additives, comprising a cover of one or both sides of a heat-resistant material, the covers being the same or different and at least one side prefabricated A microporous insulator, comprising a mica sheet. The microporous insulator according to claim 1, wherein the cover is made of a mica sheet prepared on both sides in advance. 3. The microporous insulator of claim 1 or 2, wherein said additional additive is 0-30% by weight opaque agent, 0-10% by weight fibrous material and 0-15% by weight inorganic binder. 4. The microporous insulator according to claim 1, wherein the core contains 2-45% by weight, preferably 5-15% by weight of xenonotite. The microporous insulator according to any one of claims 1 to 4, wherein the core has a thickness of 3-10 mm, preferably 5-7 mm. The microporous heat insulator according to any one of claims 1 to 5, wherein the cover is attached to the core. 6. The microporous insulator of claim 1, wherein the core and the cover are heat-sealed in a sheet. 7.